Flavonoid contributors to bitterness in juice from Citrus and Citrus hybrids with/without Poncirus trifoliata in their pedigree

Bitterness and off-flavors are problematic in some citrus genotypes, particularly <i>Citrus</i> hybrids with <i>Poncirus trifoliata</i> in their pedigrees that have shown tolerance to the devastating citrus greening disease. Comprehensive chemical profiling combined with sensory analysis of bitterness were used to determine bitter compounds in citrus juice. A selection of genotypes including orange, grapefruit, pummelo, tangelo, mandarin hybrids with and without <i>P. trifoliata</i> in their pedigrees, as well as pure <i>P. trifoliata,</i> were analyzed due to their broad range in bitterness intensity. Widely targeted LC-MS/MS analysis of flavonoids and limonoids confirmed the role of limonin, nomilin, neohesperidin and poncirin in bitterness perception. Other flavonoids, mainly rhoifolin, apigenin, and tricin also correlated with bitterness. Notably, rhoifolin was more strongly correlated with bitterness than the previously known bitter compounds. Identifying the compounds that contribute to bitterness in citrus is a crucial first step for future breeding efforts aimed at reducing these compounds biosynthetically.